Attention gadget-packing travelers: starting January 1, 2008, you will no longer be able to pack “loose lithium batteries” in your checked luggage, says the Department of Transportation. By loose, they mean either A) not attached to an electronic device in your checked luggage, or B) not in a zipped plastic baggy in your carry-on.

“Common consumer electronics such as travel cameras, cell phones, and most laptop computers are still allowed in carry-on and checked luggage,” reads the report. “However, the rule limits individuals to bringing only two extended-life spare rechargeable lithium batteries, such as laptop and professional audio/video/camera equipment lithium batteries in carry-on baggage.” Spare is the key word there.

For once, as Chris Elliott notes, this new regulation isn’t due to a terrorism threat. Instead, the ban is a safety precaution, as “lithium batteries are considered hazardous materials because they can overheat and ignite in certain conditions.”

In case the light-on-details report is unclear, this means that you can still bring your digital cameras and laptops on-board in your carry-on, but loose batteries — such as an extra one for your laptop or camera — must be limited to two, and placed in a plastic baggy if carried on. What isn’t clear is how the TSA will determine whether or not your audio, video, or camera equipment is “professional.” And if it’s not professional, is there still a limit on how many batteries you can bring on board?